An aneurysm may generally be described as a weakening in the wall of an artery or vein resulting in a bulge or bubble protruding in a radial direction relative to the adjacent vessel wall.
In the past, aneurysms have been treated through a procedure which surgically clips an aneurysm shut with a metal clip. Alternatively, the neck of the aneurysm may be clipped followed by a suture ligation of the neck of the aneurysm or the wrapping of the entire aneurysm. Each of these surgical procedures constitutes an intrusive invasion into the body for which certain areas of the body such as the brain have little tolerance. An aneurysm left untreated may rupture and hemorrhage resulting in a hemorrhagic stroke.
In the past, it has been very difficult to treat a patient having a high risk wide-neck brain aneurysm condition. In the past, a surgical procedure to treat a brain aneurysm generally involved opening the skull and the clipping of the aneurysm shut. Surgical treatments available for a brain aneurysm are frequently quite limited. In addition, brain aneurysms may be located within areas of the brain where surgical procedures will likely result in severe complications for a patient. It is therefore desirable to provide the least intrusive procedure available for treatment of a brain aneurysm which utilizes the manipulation of a catheter into the aneurysm site for occluding the aneurysm without the necessity for surgery. In the past, balloons have been used to occlude an aneurysm site or sack. A problem with the use of balloons is the risk of over-inflation which may result in the rupture of the aneurysm.
Generally, a non-intrusive treatment of an aneurysm site involves the blockage of blood flow to the aneurysm. Devices which may be referred to as vaso occlusive devices are commonly deployed to the aneurysm site through the use of a catheter delivery apparatus or introducer. One example of an implantable vaso occlusive device is a wire coil identified as a Guglielmi electrolytically detachable coil (GDC coil) which may be formed of platinum and/or nickel-titanium alloy. Devices of this nature maybe found in U.S. Pat. Nos. 4,994,069; 6,059,779; 5,643,254; 5,423,829; 6,024,754; and 5,522,822 for example.
A Platinum coil may be delivered to a treatment site by a catheter or introducer. Following release of the coil from the catheter, the coil may assume a randomly shaped mass which substantially fills the body lumen and/or aneurysm. The coil may also be coated with fibers or include a braided fibrous element to promote clotting of the blood flow proximate to the treatment site.
Alternatively, the coil may typically be formed of a platinum/tungsten alloy coil. The coils may be formed of wire having a diameter of 2 to 30 mils and is preferably flexible and soft to minimize risk of herniation of an aneurysm to be treated.
Generally, following the placement of a coil within an aneurysm a thrombus forms in the aneurysm and is followed by a collagenous material reducing the risk of aneurysm rupture.
Alternatively, a predominately platinum coil may be placed within a wide-neck aneurysm where the coil may be severed from the insertion catheter by the application of a desired and relatively small level of electrical current. In this embodiment, the coil is engaged to a guidewire through an electrolytically detachable and/or dissolvable joint. Upon exposure to the small level of current the electrolytically dissolvable joint corrodes and fails separating the platinum coil from the delivery catheter. The guidewire and/or catheter is preferably formed of a steel material and therefore functions as an anode when exposed to electrical current. The coil is generally an effective cathode when in electric contact with most metals to facilitate galvanic electrolysis at the location of the dissolvable joint.
A potential complication to be addressed during the non-intrusive treatment of a wide-neck aneurysm is the prevention of migration of a coil from the interior of the aneurysm and into a parent vessel. A need therefore exists for a stent to be positioned adjacent to the neck of an aneurysm where the stent functions to block the coil from migration out of a vessel defect. In addition, a need also exists for a stent which may remain in contact with any size of platinum coil or platinum coil mass for prevention of migration while the stent simultaneously is immune from electrolytic corrosion.
A need therefore exists for a sacrificial anode stent system which partially occludes a wide-neck aneurysm while simultaneously stenting a blood vessel adjacent to an aneurysm which is susceptible to herniation and/or rupture. Further, a need exists for a sacrificial anode stent system which facilitates the retention of an implant such as a platinum coil within the interior of the wide-neck aneurysm to occlude a desired portion of a body lumen.